The present invention relates to a multicylinder dryer of a paper machine, which comprises several successive cylinder sections of which one or more are equipped with a twin-wire draw in such a way that the web being dried is drawn between the cylinder rows unsupported, and in which a closed draw is used in section gaps in a manner such that the drying or supporting wire of the preceding section is led to touch the top cylinder of the following section at a certain small angle.
As is known, a multicylinder dryer of a paper machine comprises two rows of drying cylinders on top of each other, the web being guided zigzag over these cylinder rows. Different sections, such as wire sections and drive sections are used in the multi-cylinder dryer. In the drive sections, the rotating power is conveyed to all cylinders of the section by the same drive shaft and by a gear transmission.
In the prior art, a so called twin-wire draw is used in multi-cylinder drying sections, in which the paper web has free draws when it moves from one cylinder row to another. Also, a so-called single-wire draw is used particularly in the beginning of the multi-cylinder dryer. In such a single-wire draw, the drying wire is also arranged to support the web when it moves from one cylinder row to another. Then, the drying cylinders of one cylinder row are within the drying wire loop and the the drying cylinders of the other cylinder row are outside the drying wire loop.
Drawing the paper web over the section gaps of a multi-cylinder dryer has been a problem when using arrangements of the prior art. If a free draw is used in a section gap, the web will flutter which causes risks of breaking and worsens running ability. It also has been necessary to use a considerably high speed difference in the section gaps, which detremintally stretches the web.
Efforts have been made to solving these web drawing problems in the section gaps of a multi-cylinder dryer, with various methods such as overlapping the wire guiding rolls aimed at closing the free web draws in the section gaps. Various blow boxes have also been used. However, it has not been possible to avoid all problems or difficulties with these method. An additional difficulty has been that drawing of the end of the web has become more difficult.
Another known solution for avoiding said drawbacks has been a so-called "Pistol-Grip" draw. In this particular arrangement, the section is closed by winding the top wire of the preceding cylinder section below the bottom cylinder of the next cylinder section, and by guiding the web being supported by this top wire to the next top cylinder. The wire and the web supported by the wire are arranged to touch the top cylinder at a small angle. Even though this provides general advantages, this well-known solution has not faultlessly functioned in practice, in all respects.